Automated system for measurement of an optical property

Abstract

An apparatus for making automated measurements of an optical property of a sample includes a first stage which is movable along a predetermined line, a second stage for holding the sample, and a third stage which is movable along a predetermined line, correspondingly to the motion of the first stage. A light source is mounted on the first stage, and a light detector is mounted on the third stage. The second stage rotates the sample to a selected rotary position. The apparatus also includes a controller for coordinating movement of the first, second, and third stages such that the light source, the sample, and the light detector are optically aligned.

What is claimed is:  
     
       1. An apparatus for measuring an optical property of a sample, comprising: 
       a first stage movable along a predetermined line and having a light source mounted thereon;  
       a second stage for holding the sample and rotating the sample to a selected angular position;  
       a third stage movable along a predetermined line and having a light detector mounted thereon; and  
       a controller for coordinating movement of the first stage, the second stage, and the third stage such that the light source, the sample, and the light detector are optically aligned.  
     
     
       2. The apparatus as defined in claim  1 , wherein the controller operates the stages to measure the optical property in a predetermined pattern. 
     
     
       3. The apparatus as defined in claim  1 , wherein the first and third stages move substantially simultaneously along their respective predetermined lines. 
     
     
       4. The apparatus as defined in claim  1 , wherein the controller computes the geometric center of the sample and calculates an increment of movement of the stages. 
     
     
       5. The apparatus as defined in claim  1 , wherein the light source comprises a helium-neon laser the first stage further comprises a first linear polarizer. 
     
     
       6. The apparatus as defined in claim  1 , wherein the light detector comprises a quarter-wave plate and a second linear polarizer, the second linear polarizer mounted in a rotation stage and oriented at 90 degrees from an orientation of the first linear polarizer. 
     
     
       7. The apparatus as defined in claim  6 , further comprising means for rotating the second polarizer and means for measuring an angle of rotation of the second polarizer for determining a birefringence of the sample. 
     
     
       8. The apparatus as in claim  1 , wherein the controller is programmed to operate the stages to make measurements in substantially a spiral pattern about a cross-section of the sample. 
     
     
       9. The apparatus as defined in claim  1 , wherein the light source comprises a helium-neon laser having a wavelength of 632.8 nm. 
     
     
       10. A method for making automated measurements of an optical property of a sample, comprising: 
       moving a first stage supporting a light source and a third stage supporting a light detector to a predetermined position;  
       moving a second stage supporting the sample to rotate the sample to a predetermined angular position;  
       measuring the optical property of the sample; and  
       repeating moving the stages and measuring the optical property of the sample at spaced apart positions along a line until an edge of the sample is reached.  
     
     
       11. The method as defined in claim  10 , further comprising calculating the geometric center of the sample and determining a measurement pattern originating at the center. 
     
     
       12. A method for making automated measurements of an optical property of a sample, comprising: 
       moving a first stage supporting a light source along a line;  
       moving a second stage supporting the sample;  
       moving a third stage supporting a light detector along a corresponding line;  
       measuring the optical property of the sample with the light source and light detector to provide a plurality of optical property measurements;  
       wherein moving the second stage comprises angular rotation by an amount related to a position of the first, third stages relative to a center of the sample.  
     
     
       13. The method as claimed in claim  12 , wherein the measurements result in a spiral pattern having constant distance between points.